Access Control Essentials: Fobs, Exit Buttons, DSX & Card Readers

Quick intro: Doors not behaving? Start here before you lose more time (or access).

New key fobs won’t work—why?

Common causes:
    •    Fob format/facility code mismatch with readers
    •    Not enrolled/assigned to the user or correct access group
    •    Door on a locked (or held-unlocked) schedule
    •    Reader detects the fob but the controller denies it

Is it the fobs or the programming?

    •    Try a known-good card at the same door. If it works, the new fob likely isn’t enrolled or is the wrong format.
    •    If no cards work, check reader power and controller/door status.

Exit button won’t activate the door—what’s happening?

An exit button (REX) tells the controller or lock power supply to release.
    •    No response: REX input/wiring issue, or the lock has no power.
    •    Button LED off: check power.
    •    Lock clicks but door won’t open: strike/latch misalignment (mechanical).

What powers/activates the exit button?

Typically the access-control power supply. Pressing it triggers a REX input; the controller or relay then drops power to a maglock or energizes an electric strike to release.

DSX software isn’t working—why, and what to try

Likely culprits:
    •    Comm Server stopped or PC rebooted
    •    Database/service issue or network change
    •    License/dongle not detected (when required)
    •    Controller network unreachable

Quick triage
    •    Verify you’re on the DSX workstation with network to controllers
    •    Confirm Comm Server (and SQL if applicable) is running
    •    Check operator credentials and controller IPs
If stuck, we can remote in or visit to restore service.

Card reader not working—what powers it, and can we troubleshoot?

Readers are usually 12VDC from the controller or a dedicated supply.

Steps
    •    Present a card: does it beep/LED? If not, check power.
    •    If powered but not reading, verify format (Wiegand/OSDP) and wiring (D0/D1 or RS-485).
    •    Multiple readers down → suspect power supply or bus issue.